[Author: Sandra Álvarez-Predoctoral researcher. High Temperature Processes Unit]
Thermochemical energy storage (TCS) is a promising technology to improve the energy generation dispatchability and enhance the overall efficiency of the Concentrating Solar Power (CSP) Plants. In the frame of the European FP7 TCS Power Project; we have developed a work bench to evaluate at lab-scale, the potential of metal oxides as storing material for CSP Plants based on the technology of volumetric air receiver.
Figure 1.- CSP Plant with TCS layout.
For the high temperatures achievable in volumetric air receiver, the chemical material chosen is manganese oxide. Charging process occurs at 880-1050ºC, while discharging takes place between 520-650ºC.
Charge 3 Mn2O3 (s) + DHR → 2 Mn3O4 (s) + 1/2 O2 (g)
Discharge 2 Mn3O4 (s) + 1/2 O2 (g) → 3 Mn2O3 (s) + DHR
The developed work bench is able to operate with air flow rates up to 60 m3/h at a maximum temperature of 1000ºC. It is composed of different subsystems: dried air compressor, flow meters, air heaters, reactor, control system and hot gases exhaust.
Figure 2.- TCS work bench.
Several experiments have been performed in order to characterize the manganese oxide; from the power material to the pelletized form. We have analysed thermal diffusivity, density, hardness, ciclability under different heating rates and gases, kinetics and structural changes over the thermal treatments.
Nowadays, the experiments are in progress in the work bench and by the end of the project we would have assessed the manganese oxide potential for TCS applications.